Effect of Grain‐Boundary Phase on Dynamic Compression Fatigue in Hot‐Pressed Silicon Nitride

Abstract

Two types of hot-pressed silicon nitride, one having an amorphous grain-boundary phase (6 wt% yttria, 3 wt% alumina) and the other having a predominantly crystalline grain-boundary phase (8 wt% yttria, 1 wt% alumina), were tested on a split Hopkinson pressure bar with a momentum trap, such that, in each test, the sample was subjected to a single predefined stress pulse and then recovered without being subjected to any other loads. The specimens were loaded repeatedly with a triangular pulse of 3.2 GPa amplitude at a strain rate of approximately 400/s. The dynamic fatigue life of amorphous grain-boundary-phase silicon nitride was observed to be higher than that of the corresponding fatigue life of crystalline grain-boundaryphase silicon nitride. The difference in fatigue lives is correlated to the microstructural damage occurring in both materials.

Dense and near-net-shape fabrication of Si3N4 ceramics

“…So far, sintering of silicon nitride to high densities has demanded the addition of metal oxides [21,[143][144][145], nitrides as AlN [16,146,147] and rare earth oxides [143,[148][149][150]. According to Negita [21], an important condition for effective metal oxide sintering aids is that they do not decompose Si 3 N 4 to N 2 and SiO 2 or SiO gas in the sintering process, i.e.…”

An oscillatory pressure sintering of zirconia powder: Rapid densification with limited grain growth

“…Usually, pressureless sintering of nano‐sized ceramics particles into bulk dense bodies requires a specific green‐body microstructure that cannot be easily obtained . Pressure‐assisted sintering techniques (hot pressing, sinter forging, hot isostatic pressing, spark plasma sintering, etc.) provide an alternative approach to achieve ceramics with high density and fine grains.…”

Sintering of High‐Performance Silicon Nitride Ceramics Under Vibratory Pressure

“…Both uniaxial pressure and isostatic pressure have been extensively explored . While pressure‐assisted sintering of Si 3 N 4 has been practiced for a few decades, the current pressure‐assisted sintering methods are all conducted under constant pressure . In the previous study, we reported a novel vibration‐assisted hot‐pressing (VAHP) technique.…”

“…[8][9][10][11] While pressure-assisted sintering of Si 3 N 4 has been practiced for a few decades, the current pressure-assisted sintering methods are all conducted under constant pressure. 12 In the previous study, 13 we reported a novel vibration-assisted hot-pressing (VAHP) technique. Flexural strength of the VAHP prepared zirconia ceramic increased from 1224 MPa to 1556 MPa; also, the Y-TZP grains were confined in a narrow size range.…”